Electronic relay



1957 R. s. MARSDEM JR 2,802,155

ELECTRONIC RELAY Filed July 2, 1953 INVENTOR.

BY HJIMamdemJz:

flaw F A T TORNE Y5 United States Patent ELECTRONIC RELAY Ross S. Marsden, Jr., Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application July 2, 1953, Serial No. 365,753

7 Claims. (Cl. 317-142) This invention relates to electronic relay-s. In one specific aspect it relates to electronic relays with variable time delays. In another specific aspect it relates to electronic relays which are provided with both normally open and normally closed output terminals.

In the operation of temperature regulators and other control circuits it is generally necessary to employ a relay to energize the control circuit in response to indicated changes in the variable under control. For temperature control either a bimetallic thermoregulator or a mercury column normally is positioned in the region of temperature to be maintained and a heating element is energized as needed to maintain the desired temperature. Since temperature sensing elements of this type are not capable of carrying as large a current as is desired in the heating element, a relay is incorporated in the circuit. It has been found that commercially available relays have given consistent trouble when the sensing element is located in the presence of acid or other chemical fumes, this being due to the electrical leakage paths which are caused bythese conductive fumes or the deposits resulting from these fumes. This ditliculty has been overcome, however, by use of an electronic relay constructed in accordance with the present invention.

Accordingly, it is an object of this invention to provide an improved electronic relay which operates in a positive manner even in the presence of electrically conductive fumes.

Another object is to provide an electronic relay which is adjustable with regard to the time of operation following actuation of the input circuit.

A further object is to provide an electronic relay with both normally open and normally closed output terminals.

A further object is to provide 'an electronic relay of simple compact construction which operates in a positive manner either instantaneously or at a predetermined time interval following actuation of the input circuit.

The electronic relay of the present invention comprises generally a first vacuum tube which is biased so as to be conductive in the absence of the relay being energized. The output signal from this first tube is applied to the input circuit of a second vacuum tube which normally is biased to be non-conductive, but which becomes conductive when the first tube becomes non-conductive. The input circuit of the relay is connected to the input circuit of the first tube such that actuation of the input circuit causes the first tube to become non-conductive. A relay coil is connected in the common portion of the output circuits of the two tubes such that current is passed therethrough when the first tube is conductive, but is not passed therethrough when the second tube is conductive. This relay coil controls a pair of switches connected in respective output circuits of the relay such that both normally open and normally closed output terminals are provided. Capacitors are selectively connected in circuit with both the vacuum tubes such that a predetermined time delay can be incorporated in the relay if desired.

Other objects, advantages and features of this invention should become apparent from the following detailed description taken in conjunction with the accompanying drawing in which:

Figure l is an illustration of the assembled relay; and

Figure 2 is a schematic representation of the electrical circuit of the relay.

Referring now to the drawing in detail and to Figure 1 in particular there is shown a housing 10 which contains the various circuit components of the relay in assembled relation. A pair of leads 11 and 12 extend between housing 10 and a source of electrical energy, not shown in Figure l, which provides power for the relay circuit. A switch 13 is connected in power leads 11 and 12 to turn the relay on and off as desired. The input signal applied to the relay is connected by leads, not shown in Figure l, to a pair of input terminals 14 and 15. A first pair of output terminals 17a and 17b is provided when it is desired to have an operative output circuit with the input terminals short-circuited and a second pair of output terminals 18a and 18b is provided when it is desired to have an output circuit that is operative with the input terminals open-circuited. A switch 20 is incorporated in the relay to vary the time of response.

The electrical circuit of the relay shown in Figure 1 is illustrated in Figure 2. An external control circuit, which can be in the form of a bimetallic thermal switch 22, is connected across input terminals 14 and 15. The relay of this invention can be operated with any type of input circuit wherein a relatively small resistance bridges terminals 14 and 15 in one position and a relatively large resistance bridges input terminals 14 and 15 in a second position. The illustrated bimetallic switch is open-circuited in one position and closed in the other. The first terminal of a resistor 23 is connected to input terminal 14 and the first terminal of a resistor 24 is connected to input terminal 15, terminal 15 being maintained at ground potential. The second terminals of resistors 23 and 24 are connected to one another and to the control grid of a first vacuum tube triode 25. The control grid of triode 25 is connected to the anode of a second vacuum tube triode 26 through a resistor 27. Triodes 25 and 26 can be contained in a single envelope, as illustrated. The anode of tube 26 is connected to the anode of tube 25 through a relaycoil 28. The anode of tube 25 is in turn connected to the control grid of tube 26 through a resistor 30, and the control grid of tube 26 is grounded through a resistor 31. The cathodes of tubes 25 and 26 are grounded through a common resistor 32. A first capacitor 34 is connected in shunt with resistor 24 by a switch 20 and a second capacitor 35 is connected in shunt with resistor 31 by aswitch 20a. Switches 20 and 20a are mechanically cou'- pled to one another such that both capacitors are either connected or disconnected in unison.

Power leads 11 and 12 are connected across the terminals of a current source 37 which can provide readily available volt, 60 cycle energy. Leads 11 and 12 are 43 is grounded. The second terminal of rectifier 44 is connected to the first terminal of a filter resistor 45 and the second terminal of resistor 45 is connected to the anode of tube 26 thereby providing a source of positive operating potential. A capacitor 47 is connected betweenthe first terminal of resistor 45 and ground, and a capaci- 3. tor 48 is connected between the second terminal of resister 45 and ground. Capacitors 47 and 48 and resistor 45 thereby function as a filter to provide a steady positive potential. A lead 50 is connected between one end terminal of transformer winding 39 and a pair of switch arms 51 and 52. Switch arms 51 and 52 are mechanically coupled to one another to move in response to relay coil 28 being energized. Suitable biasingmeans, such as a spring 53, is connected to these coupled switch arms to retain the arms in a first position when not attracted by relay .coil 28; switch arm 51 engages a contact 54 when attracted by relay coil 28 and switch arm 52 engages a contact 55 when not attracted by relay coil 28. Contact 54 is connected to output terminal 18a and contact 55 is connected to output terminal 17a. A lead 56 is connected between the second end terminal of transformer winding 39 and output terminals 17b and 18b. Neon fiasher tube 19 is connected across output terminals 17a and 1715.

In describing the operation of the relay circuit it is first assumed that switches 20 and 20a are in the illustrated open positions such that capacitors 34 and 35 are disconnected from the circuit. As previously mentioned tube is' biased such as to be conductive with the input circuit of switch 22 open as illustrated. Tube 26 is biased to be non-conductive. With tube 25 conductive current passes through relay coil 28 such that switch arms 51 and 52 are in the illustrated up position. As such, output terminal 18a and 18b are connected across voltage source 37. If the temperature of bimetallic switch 22 is changed such that input terminals 14 and 15 are connected to one another through switch 22 it can be seen that the control grid of tube 25 is grounded through resistor 23 and switch 22. This resistor has a considerably lower value than resistor 24 such that the potential at the control grid of tube 25 drops sufficiently to extinguish the current flow through tube 25. The potential at the anode of tube 25 then increases to substantially the value of the potential at the second terminal of resistor 45. This in turn increases :the potential applied to the control grid of tube 26 such that this latter tube becomes conductive. As soon as tube 25 becomes non-conductive relay coil 28 is deenergized such that switch arms 51 and 52are pulled to their down position by spring 53. At this second down position output terminals 17a and 17b are connected across voltage source 37 and output terminals 18:: and 1812 are disconnected. This change is indicated visually by neon flasher '19.

If the temperature of bimetallic switch 22 varies such that the connection between terminals 13 and 14 is broken the potential at the control grid of tube 25 immediately rises such that tube 25 once again becomes conductive. This in turn lowers the potential on the control grid of tube 26 such that tube 26 once again becomes non-conductive. Conduction through tube 25 energizes relay coil 28 to restore switch arms 51 and 52 to the illustrated up position.

In some applications of this relay it has been found desirable to introduce a time delay in the operation. This is accomplished by closing switches 20 and 20a to connect capacitors 34 and in shunt with respective resistors 24 and 31. The operation previously described is then delayed by the time required for the charge to leak oif capacitors 34 and 35 during the respective operations. This time delay can be varied in accordance with the values of capacitors 34 and 35. If the time delay is desired only during the first-mentioned operation of the relay, capacitor 34 alone is connected in the circuit. If the time delay is desired during only the second-mentioned operation, capacitor 35 alone is connected in circuit.

In one specific application of the relay circuit of this invention excellent results were obtained with the following component values: resistors 27 and 30, 1 megohm; resistor 23, 220,000 ohms; resistor 24, 3.9 megohms; re-

sister 31, 560,000 ohms; resistor 32, 2700 ohms; resistor 45, 470 ohms; capacitor 34, 2.0 microfarads; capacitor 35, 1.0 microfarad; capacitor 47, 8 microfarads; capacitor 48, 16 microfarads; tubes 25 and 26 were contained in a double triode type 61 6; neon flasher 19 was type NESI; and rectifier 44 was a selenium rectifier.

The relay constructed with the foregoing component values operates if any resistance less than approximately 180,000 ohms is connected across the input terminals 14 and 15. The contact resistance of most bimetallic thermoregulators and mercury columns is considerably less than this value. The leakage resistance due to acid fumes or the like generally is considerably greater than this value.

Therefore, the relay responds only to contact closure of the control circuit. The current which flows through the contacts of the control device is of the order of microamperes. This current is sufliciently small to insure long contact life in the control switch. The time delay provided with capacitors 34 and 35 connected in the circuit-is of the order of one-half second. Such a delay has been found desirable when using the relay on some thermal regulators. This delay prevents contact chattering. and results in a more stable operation. The relay operates almost instantaneously with capacitors 34 and 35 removed from the circuit.

While this invention has been described in conjunction with a present preferred embodiment thereof it is to be understood that this description is illustrative only and that the invention is not necessarily limited thereto. The circuit values have been given for one particular embodiment of the relay and it should be apparent that other values can be selected if desired.

What is claimed is:

1. An electronic relay comprising, in combination, a first vacuum tube having at least an anode, a cathode and a control grid, a first resistor connected between the control gird of said first tube and a point of reference potential, first and second input terminals, said second input terminal being connected to said point of reference potential, a second resistor connected between the control grid of said first tube and said first input terminal, said second resistor being of lower value than said first resistor, 21 second vacuum tube having at least an anode, a cathode and a control grid, means connecting the cathodes of said first and second tubes tosaid point of reference potential, a third resistor connected between the anode of said second tube and the control grid of said first tube, a relay coil connected between the anode of said first tube and the anode of said second tube, a fourth resistor connected between the anode of said first tube and the control grid of said second tube, a fifth resistor connected between the control grid of said second tube and said point of reference potential, output switching means actuated by said relay coil, a source of potential which is positive with respect to said point of reference potential, and means connecting said source of potential to the anode of said second tube, the values of said resistors and the magnitude of said source of potential being such that said first tube is conductive and said second tube is non-conductive when the impedance applied across said input terminals is in excess of a predetermined value, and said second tube is non-conductive and said first tube is conductive when the impedance connected across said input terminals is less than said predetermined value.

2. An electronic relay comprising, in combination, a first vacuum tube having at least an anode, a cathode and a control grid, :1 first resistor connected between the control grid of said first tube and a point of reference potential, first and second input terminals, said second input terminal being connected to said point of reference potential, a second resistor connected between the control grid of said first tube and said first input terminal, said second resistor being of lower value than said first resistor, a second vacuum tube having at least an anode, a cathode and a control grid, means connecting the cathodes of said first and second tubes to said point of reference potential, a third resistor connected between the anode of said second tube and the control grid of said first tube, a relay coil connected between the anode of said first tube and the anode of said second tube, a fourth resistor connected between the anode of said first tube and the control grid of said second tube, a fifth resistor connected between the control grid of said second tube and said point of reference potential, a source of potential which is positive with respect to said point of reference potential, means connecting said source of potential to the anode of said second tube, a source of voltage, a first pair of output terminals, first and second leads connecting said first pair of output terminals across said source of voltage, a first switch connected in said first lead, a second pair of output terminals, third and fourth leads connecting said second pair of output terminals across said source of voltage, a second switch connected in said third lead, said first and second switches being actuated by said relay coil, and means coupling said first and second switches whereby said first switch is closed and said second switch is open when said relay coil is energized, said first switch being open and said second switch being closed when said relay coil is not energized, the values of said resistors and the magnitude of said source of potential being such that said first tube is conductive and said second tube is non-conductive when the impedance applied across said input terminals is in excess of a predetermined value, and said second tube is non-conductive and said first tube is conductive When the impedance connected across said input terminals is less than said predetermined value.

3. The combination in accordance with claim 1 further comprising a capacitor, and means to connect said capacitor in parallel with one of said first and fifth resistors.

4. The combination in accordance with claim 1 further comprising a first capacitor connected in parallel with said first resistor, and a second capacitor connected in parallel with said fifth resistor.

5. The combination in accordance with claim 2 further comprising a capacitor, and means to connect said capacitor in parallel with one of said first and fifth resistors.

6. The combination in accordance with claim 2 further comprising a first capacitor connected in parallel with said first resistor, and a second capacitor connected in parallel with said fifth resistor.

7. An electronic relay comprising a first vacuum tube triode, a first resistor connected between the control grid of said first triode and ground, first and second input terminals, said second input terminal being connected to ground, a second resistor connected between the control grid of said first triode and said first input terminal, said second resistor being of lower value than said first resistor, 21 second vacuum tube triode, a third resistor connected between the anode of said second triode and the control grid of said first triode, a fourth resistor connected between the cathode of said first triode and ground, the cathode of said second triode being connected to the cathode of said first triode, a relay coil connected between the anode of said first triode and the anode of said second triode, a fifth resistor connected between the anode of said first triode and the control grid of said second triode, a sixth resistor connected between the control grid of said second triode and ground, a source of voltage having the positive terminal thereof connected to the anode of said second triode, the negative terminal of said source of voltage being connected to ground, a first capacitor connected in parallel with said first resistor, and a second capacitor connected in parallel with said sixth resistor, the values of said resistors and the magnitude of said source of voltage being such that said first triode in conductive and said second triode is non-conductive when an impedance applied across said input terminals is in excess of a predetermined value, said first triode becoming non-conductive and said second triode becoming conductive when an impedance connected across said input terminals is less than said preselected value.

References Cited in the file of this patent UNITED STATES PATENTS 2,475,050 Purington July 5, 1949 2,524,300 Taylor Oct. 3, 1950 2,596,956 Nierman May 13, 1952 2,664,489 Dickey Dec. 29, 1953 

